We are in the midst of a blossoming of essays on Don Quixote, marking the 400th anniversary of the publication of Part One in 1605. Part Two followed 10 years later, and one of the unique features of Cervantes's novel is that there are characters in Part Two who know all about Don Quixote and his squire before they meet them, because they have already read Part One. Part One is indeed often taken to be essential Quixote, and several of the famous incidents occur early in its pages.

If, by any chance, you are thinking of marking the anniversary by reading the book, I have a small and obvious recommendation. Get hold of a copy of Vladimir Nabokov's "Lectures on Don Quixote". One might object that Nabokov was a powerful intellect, and the last thing one wants, on encountering Cervantes for the first time, is another quite distinct intellectual or artistic presence, to distract from a fresh reading of the masterpiece.

If that is so, so be it. But a part of what made Nabokov distinctive as a lecturer (on this subject at least) was his helpfulness towards his students, even on matters that may seem obvious to us. He insisted, we are told, "that they knew what a windmill was, and drew them one on a blackboard, and instructed them in the names of its parts. He told them why a country gentleman might mistake them for giants — they were an innovation in seventeenth-century Spain."

The students in question were at Harvard in 1951-1952, and in Cornell from 1948-1959. No doubt they were not stupid, but some of the critical authorities they would otherwise have read undoubtedly were stupid. Nabokov, who did withering exceptionally well, is withering about them. Among the numerous misconceptions about Don Quixote is the idea that the knight never wins any of his contests: he always ends up with a drubbing. But that is not true at all.

In one lecture Nabokov goes through the contests one by one, and scores them, finding that the tally is even: the Don wins as many contests as he loses. "Moreover," says Nabokov, "in each of the two parts of the book the score is also even: 13 to 13 and 7 to 7, respectively. This perfect balance of victory and defeat is very amazing in what seems like such a disjointed and haphazard book. It is due to a secret sense of writing, the harmonizing intuition of the artist."

One may quibble with Nabokov's scoring, but I doubt that his students will have forgotten the key point being made, that there is a secret sense at work, an intuitive balance of give and take. Those who know Don Quixote only through its innumerable offspring are in for some surprises should they actually read the book. The Don dies disillusioned and repentant of his quest, something that was not allowed to happen at the end of The Man of La Mancha

WH Auden, who was commissioned, with Chester Kallman, to write the lyrics for the musical, based on a television play by Dale Wasserman, fell out with the author of the "book" on this point, as Wasserman himself recalled. What Wasserman wanted was for Auden to write the lyric which eventually became "Impossible Dream". But Auden wrote something diametrically opposed. Here's how the argument went, as recounted by Wasserman:

"Your words are existentialist," I argued.

"They are also fatalistic."

"They are the proper words for Don Quixote."

"They are not for Dale Wasserman."

Still we might have reconciled our differences but for the play's finale. Here Auden was adamant: Quixote must repudiate his quest and warn others against like folly.

I said no, in thunder.

"Wasserman, the man was mad."

"It's a madness we happen to need."

"That is arrant romanticism."

"I know, but it happens to be my thesis."

Quite how Auden and Wasserman would have sorted out the Dulcinea problem, had they not fallen out over the Impossible Dream problem, is not clear. Auden would definitely have wanted to follow Cervantes, as in the surviving "Song of the Knight of the Mirrors":

Look! Those noble knights of oldWere, when the whole truth is told, All crooks.Look at Dulcinea! Mutt!She's the common kitchen slut She looks.

What Wasserman wanted was what Wasserman got: a Tart with a Heart of Gold. But in the narrative of Don Quixote we never meet Dulcinea, although the Don himself claims to have done so in the Cave of Montesinos (an ambiguous episode, about which he seems to have come close to lying).

I don't say that Nabokov is the perfect guide. He seems to me to have a down on Sancho Panza - clearly a handicap for a critic of Cervantes, who appears to have started his story without any idea that Sancho Panza was going to exist, but then, having once invented him, realised that he was the key to the whole comic scheme. But the lectures, which are based on Nabokov's unrevised notes, give you a thrilling sense of what the performance must have been like. And there's a handy, complete plot summary, should you need a crib.